docs: def add_argument(self, *args, **kwargs):
      """
      This method supports the same args as ArgumentParser.add_argument(..)
      as well as the additional args below.
  
      Additional Args:
          env_var: If set, the value of this environment variable will override
              any config file or default values for this arg (but can itself
              be overriden on the commandline). Also, if auto_env_var_prefix is
              set in the constructor, this env var name will be used instead of
              the automatic name.
          is_config_file_arg: If True, this arg is treated as a config file path
              This provides an alternative way to specify config files in place of
              the ArgumentParser(fromfile_prefix_chars=..) mechanism.
              Default: False
          is_write_out_config_file_arg: If True, this arg will be treated as a
              config file path, and, when it is specified, will cause
              configargparse to write all current commandline args to this file
              as config options and then exit.
              Default: False
      """
  
      env_var = kwargs.pop("env_var", None)
  
      is_config_file_arg = kwargs.pop(
          "is_config_file_arg", None) or kwargs.pop(
          "is_config_file", None)  # for backward compat.
  
      is_write_out_config_file_arg = kwargs.pop(
          "is_write_out_config_file_arg", None)
  
      action = self.original_add_argument_method(*args, **kwargs)
  
      action.is_positional_arg = not action.option_strings
      action.env_var = env_var
      action.is_config_file_arg = is_config_file_arg
      action.is_write_out_config_file_arg = is_write_out_config_file_arg
  
      if action.is_positional_arg and env_var:
          raise ValueError("env_var can't be set for a positional arg.")
      if action.is_config_file_arg and not isinstance(action, argparse._StoreAction):
          raise ValueError("arg with is_config_file_arg=True must have "
                           "action='store'")
      if action.is_write_out_config_file_arg:
          error_prefix = "arg with is_write_out_config_file_arg=True "
          if not isinstance(action, argparse._StoreAction):
              raise ValueError(error_prefix + "must have action='store'")
          if is_config_file_arg:
                  raise ValueError(error_prefix + "can't also have "
                                                  "is_config_file_arg=True")
  
      return action